1. Field of the Invention
The present invention concerns a prosthetic device for creating a vascular bypass, without clamping, from a blood vessel, in particular from the aorta, which may have significant collateral branches. More particularly, the invention relates to a prosthesis for vascularization of the collateral branches of the aorta, without clamping, that is, without interrupting blood flow within it by means of occlusive forceps or clamps, or other means.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
For this purpose, whenever we wish to supply blood to an artery that emerges from the aorta because it is more or less completely occluded, several procedures are used, more or less preferentially, depending on the pathological circumstances.
When the artery presents a stricture or isolated and short occlusion, a method using balloon dilatation together with the insertion of an endoprosthesis, is recommended. This endoprosthesis (still referred to as a stent) is a kind of mesh tube intended to keep the dilated area that was the site of the lesion permeable. This method is noninvasive. It involves the use of catheters introduced into the arteries, most frequently under local anesthesia. There is no surgical incision. Bleeding is practically nonexistent.
The disease is often more developed, affecting a considerable length of a branch of the aorta, or several branches, and may even affect the portion of the aorta from which those branches emerge. It may then be necessary to supply blood to the organs irrigated by this, or these, artery(ies) through the use of one or more vascular bypasses originating at the aorta. These bypasses consist, in general, of prosthetic conduits. They allow lesions to be short-circuited. One of the ends of the prosthetic conduit, known as the proximal end, is sewn to the aorta. This is the extremity that captures the blood. The other extremity, known as the distal end, is sewn to the branch of the aorta downstream from the lesions. It is this extremity that distributes the blood. The sewn areas are referred to as anastomosis.
Proximal anastomosis of the aorta is performed by sewing the prosthetic tube to an orifice cut in the wall of the aorta. This orifice, specifically known as an aortotomy when it involves the aorta, must be isolated from circulation for as long as it is being sewn to avoid bleeding. To do this, circulation in the aorta is stopped by means of special forceps known as clamps. Clamping may either be total, in which case circulation is completely stopped, or partial, which allows some blood to flow to those areas located downstream. Similarly, distal anastomosis of the collateral branch occurs by isolating from circulation the segment of the artery that is the site of the anastomosis and by making an opening therein or by sectioning.
These bypass procedures have existed for several decades. They necessitate:
First, a surgical incision of the abdominal wall and/or thoracic wall, depending on circumstances, to access the aorta and, sometimes, another incision (or several) to access the branch (or branches) one wishes to revascularize.
Second, partly or completely stopping circulation in the aorta to make the suture or anastomosis of the prosthetic tube at that location. Any complete or partial stoppage of circulation in the aorta will have significant hemodynamic and metabolic repercussions on all organs located downstream and upstream.
Downstream: the organs will be more or less completely deprived of blood and, therefore, of oxygen, for the entire duration of the anastomosis. This cessation of circulation is more or less harmful depending on where the cessation of circulation occurs.
For example, stopping circulation at the terminal part of the aorta located in the abdomen can easily be tolerated for several hours. Downstream, there remain only the inferior members and the organs of the minor pelvis, which are relatively insensitive to what is referred to as the absence of circulation or ischemia (oxygen deprivation).
However, as circulation is stopped higher (upstream) on the aorta, tolerance is reduced.
Therefore, if circulation is stopped near the lower part of the thorax, a portion of the spinal cord is deprived of arterial blood, as well as all the organs located in the abdomen, such as, for example, the kidneys, liver, and digestive tract. These organs can support ischemia for no more than some tens of minutes at the most. Consequently, the time during which the anastomosis can be carried out is very limited.
The most harmful consequences are found when circulation is stopped near the origin of the aorta, just after it emerges. In addition to depriving the other areas previously mentioned, which are located downstream, this portion of the aorta gives rise to arteries that irrigate the brain. These arteries can tolerate no more than two or three minutes of circulatory arrest, which makes it impossible to carry out the anastomosis. Consequently, circulation can only be stopped in this region by making use of techniques of extracorporal circulatory assistance involving the use of machines. Such means, used during suturing, continue to provide blood to the brain and to the areas previously mentioned in order to eliminate the deleterious effects of stopping circulation in the aorta to implant the prosthetic bypass. Unfortunately, such techniques of circulatory assistance are complicated. They are in themselves the cause of inherent complications and significant mortality.
Upstream, the consequence of interrupting arterial flow results in hypertension, which is manifested in the region situated above. As with ischemia, hyperpressure increases the higher up one works. It makes the heart work harder.
Third, suturing the prosthetic tube and aorta wall edge to edge with a very fine thread. When circulation is restored to the attachment area, there is a risk of hemorrhage. For, it is rare for a suture to be initially leakproof and circulation must often be interrupted again and stitches added to the suture. This factor needs to be examined very carefully today because of the frequency of antiaggregating and anticoagulating treatments that are practically ubiquitous and prescribed for life for patients afflicted by cardiovascular diseases. These treatments, which increase the risk of bleeding, cannot always be stopped during the operation.
On the other hand, we note that this type of edge-to-edge suture has other drawbacks, especially over the long term. The suture is continually subject to arterial pressure with a momentary increase 70 times a minute due to the contraction of the heart. Occasionally there are tears, either in the aorta wall or in the prosthesis, with separation of the connection between artery and prosthesis. This separation, once begun, will continue to develop through the effect of arterial pressure. In approximately 2% of cases it leads to the formation of a false aneurysm that most often requires a new operation.
Fourth, suturing the distal end of the prosthetic tube on the collateral branch or branches for which blood is destinated. This part of the operation is less traumatic than the aortic suture.
Prosthetic devices have been proposed to facilitate anastomosis and limit certain risks (FR-2799362, EP-0269254, U.S. Pat. No. 6,273,912, WO-2006/013234, FR-2751867). These devices comprise a prosthetic tube, generally made of a synthetic textile compatible with biological tissues and, therefore, referred to as “biocompatible,” that may or may not include one or more ramifications, and is equipped, at its extremities, with a collar suitable for anastomosis of said prosthetic tube on an organic conduit such as an artery (aorta or other) and/or a vein. These collars allow the prosthesis to be attached to one or two organic conduits by means of a conventional suture or by using clips or staples opposite openings (arteriotomies) made in said organic conduit or conduits. In all cases, the inner face of these collars is in contact with the interior of the blood vessel and the circulating blood.
However, the operating procedure employing these prosthetic devices always requires clamping or the interruption of blood circulation in the portion of the anatomical conduit in which the prosthesis is to be implanted, along with the serious consequences this may entail, while the risk of peroperative and postoperative bleeding remains significant.
An object of the present invention consists of a prosthetic device that can be attached to an artery, in particular to the aorta, without the clamping that stops circulation and without the risk of peroperative and postoperative bleeding.